Book 37: "The Naked Sun" by Isaac Asimov

[kittiwake]

When Detective Elijah Baley is summoned to Solaria to investigate a murder, he is the first earthman to visit the Outer Worlds in centuries. Each of the twenty thousand Solarians live on a huge estate maintained by robots, and although they all know each other and socialise by 'viewing' each other via tri-dimensional viewer, they are phobic about personal contact, and it is only husbands and wives who, reluctantly, 'see' each other in person. None of the Solarians can understand how the murderer and his/her victim could have stood being in each others' presence long enough for the murder to occur, but they are all convinced that the only possible suspect is the victim's widow. Baley finds it very hard to understand their phobia, just as they can’t understand his phobia of being outside. The Aurorans have sent R. Daneel Olivaw to work with him, as they believe that there could be a motive behind the murder that could threaten the future of the human race both on the Outer Worlds and Earth itself, but the robot's need to protect Baley from harm threatens to scupper the murder investigation.

Another re-read.